Using Staphylococcus aureus as an example, this solution gives a detailed description of how a person's innate and adaptive immune system would fight off this potentially life-threatening infection. This includes details of recognition by pattern recognition receptors, macrophages and dendritic cells, the important cytokines and other soluble factors and the function of lymphocytes in the immune response. It also describes when should person seek medical care and describe diagnosis treatment for this infection.
When bacteria are first encountered by the immune system, one of the first cell types to counter the infection is the neutrophil. These cells recognize bacteria by means of cell surface receptors such as mannose receptors, that bind onto common pathogen-associated molecules such prokaryotic carbohydrates. Both neutrophils and macrophages will phagocytose the bacteria, taking them into intracellular vesicles where they can be destroyed. Phagocytes release several antimicrobial substances into the phagocytic vesicle, for example enzymes such as lysozyme and cathepsins, that attack the bacterial cell walls. Phagocytes also release reactive oxygen and nitrogen species into the vacuole, which are toxic for the bacteria.
Bacteria in the tissue can activate the alternate pathway of complement activation, as the bacterial cell surface can stabilize the C3Bb convertase, that triggers complement cascade by cleavage of further C3 molecules. During the proteolytic cascade, large amounts of C3b are generated, that covalently bind onto the bacterial cell surface. The C5 component of complement is then activated, as it binds onto C3b and becomes a substrate for C3Bb, which release C5a and C5b. C5b also binds to the bacterial cell surface. C5b subsequently binds C6, C7 and C8 to form a complex that can orientate correct insertion of C9 into the bacterial cell membrane, forming a pore ...
This solution describes the initiation of an innate immune response against bacterial infection (Staphlococcus aureus). It also describes the clinical presentation and diagnosis of this infection.